For years, eagle-eyed conspiracy theorists have been trawling through the photos beamed back to Earth by NASA probes and “discovering” mysterious objects that they say proves the existence of extraterrestrial activity on Mars — a world where lizards, mermaids, traffic lights, jelly donuts and a statue of Barack Obama all apparently coexist in the dusty expanses of the red planet. In reality they’re probably all just weirdly shaped rocks, but why spoil the fun?

The latest arrival, as it were, is the sighting this week of a spaceship — or at least a spaceship-shaped rock — that UFO buffs believes crash-landed on Mars.

“I found this anomaly in the latest Curiosity Rover photo. The black object looks like a crashed UFO,” writes Scott C. Waring on the UFO Sightings Daily website.

“The craft is only about 2.5-3 meters across, so it probably only held a few passengers. Since many of the figures we found on Mars are about 5-8 cm tall, then we can conclude that his [sic] ship could carry about 20-40 passengers.”

Far out indeed, but not as far out as the discovery of a giant Martian crab in early August. Or the “strange woman” peering down at the Curiosity rover last month. Or the levitating rock in June. You get the idea.

But let’s not trade our tin foil hats for helmets and prepare for Mars to attack just yet. One NASA scientist says there’s a perfectly good explanation for these sightings.

“We have color HD cameras on this rover that far exceed anything ever sent to the planet before, and yet in order to find these things that kind of trick your brain into thinking it’s a mermaid or whatever, you do have to zoom in where it’s kind of a fuzzy shadow at that point,” Ashwin Vasavada, a scientist who works on the Mars rover project, told CNN.

Vasavada is alluding to a phenomenon called pareidolia, which is when your brain recognizes a familiar object or pattern even though it’s not actually there. It explains why people see the Man in the Moon, Jesus in their lunch, or even a tiny woman wandering around Mars.

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Vasavada remembers her well. “That photo was up in a place we are studying,” he says, “a place we call a ‘geologic contact’ where there is a lot of sandstone next to mud that formed at the bottom of an ancient lake.”

“Now, three billion years after that happened, little drifts of sand are following down the hill … when you zoom in and kind of look at the light and shadows, it does look like a little figure of a woman,” he admits. “But she would be a few inches tall and hasn’t moved in months, so we don’t think that’s what it is.”

Vasavada enjoys the things people claim to see in Curiosity’s photos, but says his team doesn’t take it too seriously. And he’s as hopeful as everyone else is that NASA will find evidence of intelligent life on Mars.

“There is no group that would be (happier) to see such a thing than the 500 scientists around the world who work on this Curiosity rover,” he says. “So far we haven’t seen anything that is so obvious that it would be similar to what these claims are.”

But what about the space rat that’s so obviously crouched amidst the rubble in this photo? Here’s Vasavada to ruin the party again.

“We have no evidence of Martian iguanas or rats at this time,” he says. “One of the best things we found is that Mars could support life, (but) if anything we think it’s microbial life that’s possible at this time. Things like rats and iguanas would be way further up the food chain that we think Mars may have ever gotten to.”

Rats, iguanas and tiny women aside, amateur speculation over the Mars photos hasn’t all been in vain. Just the other day, Vasavada says someone on the Internet “found a place where a meteor had struck Mars while we were there roaming, so that is pretty fantastic.”

For Vasavada, the weirdest thing about the thousands of photos taken by Curiosity is how they’re not really weird at all.

“The thing that keeps coming back to me every single day is how un-weird it is, how much it looks like Earth,” he says. “It’s just fascinating that (on) Mars, even today, you can see the landscapes formed in similar ways that deserts and other places on Earth formed. It’s kind of mind-blowing.”

Not as mind-blowing a find as a Martian, of course. But Vasavada urges patience.

“We are working our way to answering what is a very difficult scientific question,” he says. “It’s unfortunately not going to be as easy as seeing a mermaid in a picture.”